util/IMdkit: Fix the range of memset() in i18nIc.c
util/IMdkit: Fix the range of memset() in i18nIc.c

BUG=https://github.com/ibus/ibus/issues/1891

Review URL: https://codereview.appspot.com/320010043

fujiwarat/ibus,Keruspe/ibus,ibus/ibus,fujiwarat/ibus,Keruspe/ibus,ibus/ibus,fujiwarat/ibus,Keruspe/ibus,ibus/ibus,fujiwarat/ibus,Keruspe/ibus,ibus/ibus